Optical imaging is a non-invasive imaging modality that can visualize functional dynamics of blood volume and oxygen consumption associated with brain physiology and pathology. The Culver group has developed a novel high-density diffuse optical tomography (HD-DOT) system that achieves fMRI-comparable image quality and sensitivity and can detect cortical resting state networks (RSN) using functional connectivity and cortical blood flow responses to tasks. This technological innovation now opens up new avenues of research into patient populations that cannot be imaged with fMRI. A prime example of this new opportunity is individuals with implanted deep brain stimulators (DBS). The systems-level impact of DBS responsible for clinical benefit and potential side-effects is still not fully understood and could be useful in optimizing DBS, potentially providing short-cuts to the current trial-and-error approach to programming and electrode selection. Currently, investigations into the brain networks involved in DBS are difficult due to the significant limitations of conventional neuroimaging techniques. Due to contraindications from implanted hardware, these patients cannot be safely imaged with MRI for research purposes. Although blood flow can be measured by PET in these patients, studies are limited due to radiation exposure limits and poor temporal resolution (e.g. minutes). In contrast, HD-DOT allows us to measure cortical hemodynamics in response to task or DBS conditions and measure resting state networks with comparable temporal and spatial resolution to fMRI and with greater comfort (patients sit in a comfortable chair during scanning) and no radiation exposure. We have previously shown the feasibility of assessing cortical RSNs and task-induced responses in a small number of patients with subthalamic nucleus (STN) DBS. The work proposed here will establish the utility and sensitivity of HD-DOT to answer important clinical and theoretical questions in two different DBS populations.